ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



113 



Society screw. The stage lies in the same plane as the centre of 

 movement for mirror ; it is of brass, and has concentric revolving 

 motion. The mirror-bar swings upon one bearing, to any obliquity 

 below and above the stage for the illumination of opaque objects, and 

 has attached to it a secondary bar, to which the mirror is fitted, and 



Fig, 



which allows the separate use of the latter in any position of the sub- 

 stage. It is provided with a sliding arrangement, whereby the mirror 

 may be moved to and from the object. The substage is adjustable 

 along the mirror-bar, and entirely removable. It contains a diaphragm 

 which may be brought directly under the stage. The ring is of 

 standard size, and is centered by a set-screw." 



Ser. 2.— Vol. I. I 



